A Compact Dual-Core 26.1-to-29.9GHz Coupled-CMOS LC-VCO with Implicit Common-Mode Resonance and FoM of-191 dBc/Hz at 10MHz

Abstract

A compact dual-core, single-transformer, and low-power voltage-controlled oscillator (VCO) is presented. The single transformer provides resonance at both differential and common modes, eliminating the need for an explicit inductor for the common-mode resonance. It is implemented vertically using two top metal layers, resulting in significant area saving compared to the state-of-the-art. The LC-tank has common mode resonance at twice the VCO frequency, hence reducing the flicker noise corner frequency of the VCO to 450 kHz. A fully-balanced complementary coupled-Class-C design improves efficiency, maintains symmetric swings across the transformer, and improves reliability. A prototype 26.1-to-29.9 GHz VCO, suitable for 5G applications, is implemented in a 65-nm CMOS process occupying an area of 0.04 mm2. The VCO consumes 3.4 mW at 27.45 GHz and exhibits a phase noise of -127.5 dBc/Hz at 10 MHz offset resulting in an FoM of -191 dB/Hz.